Although Qingyu currently only displayed a realm at Soul Formation Peak, with his mastery of the Great Dao Force, eliminating cultivators at the Dao Integration stage was effortless. His baseline strength was already formidable, and bolstered by the Great Dao Force, he was even more powerful. Even without the Great Dao Force, Qingyu could have wiped out everyone in the Feixian Sect, though it would not have been quite as easy—requiring at least two attacks.
Now, however, a single strike was enough.
As for why he spared the Feixian Sect Master, it was because Qingyu wanted to see what secrets the master was hiding. From the original text, Qingyu knew very well that the Feixian Sect Master, Zheng Yumen, practiced a technique that burned his life force to break through to the Dao Integration stage. In reality, the Dao Integration stage he reached was not a true Dao Integration stage; it merely possessed the aura and a fraction of the power of one.
Chapter 185